Evaluation of seismic reliability of steel moment resisting frames rehabilitated by concentric braces with probabilistic models

Abstract

Probability of structure failure which has been designed by "deterministic methods" can be more than the one which has been designed in similar situation using probabilistic methods and models considering "uncertainties". The main purpose of this research was to evaluate the seismic reliability of steel moment resisting frames rehabilitated with concentric braces by probabilistic models. To do so, three-story and nine-story steel moment resisting frames were designed based on resistant criteria of Iranian code and then they were rehabilitated based on controlling drift limitations by concentric braces. Probability of frames failure was evaluated by probabilistic models of magnitude, location of earthquake, ground shaking intensity in the area of the structure, probabilistic model of building response (based on maximum lateral roof displacement) and probabilistic methods. These frames were analyzed under subcrustal source by sampling probabilistic method "Risk Tools" (RT). Comparing the exceedance probability of building response curves (or selected points on it) of the three-story and nine-story model frames (before and after rehabilitation), seismic response of rehabilitated frames, was reduced and their reliability was improved. Also the main effective variables in reducing the probability of frames failure were determined using sensitivity analysis by FORM probabilistic method. The most effective variables reducing the probability of frames failure are in the magnitude model, ground shaking intensity model error and magnitude model error

Keywords

• seismic reliability
• steel moment resisting frame
• rehabilitation
• probabilistic model